Nay on plastic bags, and yea on solar subsidies and biofuel buses: Anyone see a pattern here? San Francisco is cleaning up its environmental act. A further effort to compost garbage makes sense.

The city already has one of the highest rates of recycling and composting in the country, diverting 72 percent of its garbage from dumps. That means fewer disposal sites, less pollution and fuel consumption by dump trucks, and more soil-enriching compost.

On pickup day, many residents already roll out three bins - blue for recycling, black for throwaways and green for composting garden and kitchen waste. The city is headed in the right direction of reclaiming waste, and it's time to do more.

Much is made about penalizing folks who don't get with the program. The fines could hit $500 for a garbage tosser who doesn't heed the message after repeated warnings. But this heavy whack isn't likely to happen casually, because garbage collectors and city officials believe residents will cooperate once the procedures are explained.

The initiative rests on fairness and public education. The city will need to spread the word in coming months to inform residents, businesses and landlords, who aren't already using the green bin. Garbage firms plan to do the same.

San Francisco already has shown an aptitude for doing the right thing. It's time to nudge the city forward. Mayor Gavin Newsom's proposal, backed by the Board of Supervisors, broadens a plan that's working well.